String Index out of bounds error, basic program

Question

This program does what I want it to do but it also outputting a massive big error. Which says something like "array out of bounds. string index out of bounds". The program is meant to take an input of a sentence and rewrite it using different letters (4 characters up) from the alphabet. Please help me clear up this error!

public class Encryption
{
public static void main (String [] args)
{
System.out.print("Enter a message to encrypt: ");
String input = Console.readString();

for(int i = 0; i<100; i++)
{
char oldChar = input.charAt(i);

char encryptedChar = (char) (oldChar + 4);

System.out.print(encryptedChar);
}   
}

Answer 1

If you get a StringIndexOutOfBoundsException , then your input isn't 100 characters long.

Don't expect 100 characters; stop your for loop when i reaches your string's length.

for (int i = 0; i < input.length(); i++)

Answer 2

Is the input always a 100 character string, I believe not and that's the error. Replace 100 with input.length()

Answer 3

Change your loop bounds. You're looping from i=0 to i=99 which will exceed the input length if the user types less than 100 characters.

for (int i = 0; i < input.length(); i++)

Answer 4

As previously stated you hard coded the loop to iterate 100 chars. What if the string isn't 100 char